Method of coating a retroreflector to avoid reflecting visible light

ABSTRACT

This describes an enhanced retro-reflector that is designed to be a retro-reflector of non-visible light, but not visible, and can be designed to resemble common dust or dirt in the visible spectra. As the beads retro-reflect very little visible light they are not easily seen in visible light; thus they are difficult to counterfeit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/385,294, filed Sep. 22, 2010, the contents of which isincorporated by reference herein in its entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates in general to the field of enhancedretro-reflector, and in particular, an apparatus and method thatdescribe an enhanced retro-reflector that is designed to be aretro-reflector of non-visible light, but not visible, and can bedesigned to resemble common dust or dirt in the visible spectra.

BACKGROUND OF THE INVENTION

A retro-reflector is a device that sends light or other radiation backtowards the direction it came from regardless of the angle of incidence,unlike a mirror, which does that only if the mirror is exactlyperpendicular to the light beam. This effect can be commonly obtained intwo ways: with a series of three perpendicular mirrors (a cornerreflector), a sphere of material with refractive index different fromthe surrounding media and/or other properly designed geometries.

Retro-reflection is used on road surfaces, road signs, vehicles andclothing (large parts of the surface of special safety clothing, less onregular coats). When lights illuminate a retro-reflective surface, thereflected light is directed generally towards the source, and not highlywasted by going in all directions as with diffuse reflection.Retro-reflectors can approach efficiencies greater than 60%. Cornerreflectors are better at sending the light back to the source over longdistances, while spheres are better at sending the light to a receiversomewhat off-axis from the source.

In 1942, Engineering News—Record wrote, “Paint surfaced with reflectivebeads has been found superior to any other type painted pavement markingFive hundred miles of this type have been laid in Philadelphia and foundto be very satisfactory. Although glass-beaded paint costs more,experience shows that it wears four to five times as long.” Whenreflectorized paint was first introduced, the greater durability of thepaint line made the reflectorized paint more cost effective. Today,reflectors are used on center and edge lines for greater safety.

FIGS. 1 and 2 illustrate the difference between using pavement markingswith and without reflective beads. FIG. 1 shows prior art pavementmarkings with uncoated retro-reflective beads at night when illuminatedwith visible light from automobile headlights. FIG. 2 shows prior artpavement markings without reflective beads at night when illuminatedwith visible light from automobile headlights. By comparing FIGS. 1 with2, it can be seen that the use of even uncoated reflective beads makes adramatic difference. The two center lines here reflected yellow light,as the uncoated beads were embedded in yellow paint. Up to 80% of thesignal can be reflected back to source with a 60° from normal acceptanceangle.

Unbeaded paint lines will reflect light randomly in all directions. Whenround reflective beads are added, light is reflected and directed towardthe source of the light.

Hence, a retro-reflector is a device that sends light or other radiationback where it came from regardless of the angle of incidence, unlike amirror, which does that only if the mirror is exactly perpendicular tothe light beam. This effect can be commonly obtained in two ways: with aset of three perpendicular mirrors (a corner reflector) and with atransparent sphere of material with refractive index. A retro-reflectormay consist of many very small versions of these structures incorporatedin a thin sheet or in paint. In the case of paint containing glassbeads, the paint glues the beads to the surface where retro-reflectionis required, and the structure protrude, about twice the thickness ofthe paint. A third, much less common way of producing a retro-reflectoris to use the nonlinear optical phenomenon of phase conjugation. Thistechnique is used in advanced optical systems such as high-power lasersand optical transmission lines.

When light strikes a non-corner reflector retro-reflector it isrefracted and reflected. Refraction is the bending of the light.Refraction is observed when a pencil is dropped into a half filled glassof water; the pencil appears bent. Reflective retro-reflector's abilityto bend light is measured by its index of refraction, which is a ratioof the sine of the angle of incidence to that of the refraction. Theretro-reflectivity of glass beads is better explained by examining thepath of light as it enters a single retro-reflector in the paint (FIG.3). There are actually millions of tiny retro-reflector in each deliveryelement that perform this principle.

As the laser beam enters the retro-reflector, it is bent or refracted.This beam then shines on the back surface of the retro-reflector, whichis on top of the paint, thermoplastic, etc. The paint works a lot like amirror. If the paint were not present, most of the light would continuethrough the bead and bounce in several directions. This is one reasonwhy the retro-reflectors are often placed in a polypropylene paint up toone half of the retro-reflector. The light is bent (refracted) by thecurved surface of the retro-reflector to a point below where theretro-reflector is sunk into the paint. Thus, when light is reflectedoff the paint at the back of the reflectors a large portion of thatlight is reflected through the retro-reflector and refracted back towardthe light transmitter.

The amount of refraction of light is characteristic of the glass itselfand is known as the index or refraction (n) of the glass, bead,particle, or phosphor. The refractive index of the retro-reflector isdependent upon the chemical and physical make-up of the glass material.Various types of retro-reflectors have different indices of refractionand cause different amounts of light to be retro-reflection or returnedto the receiver/laser transmitter.

Water has an index of refraction of 1.33, while the typical bead madewith soda glass has a refractive index of 1.50. Beads used in thepavement marking industry are available in refractive indexes of 1.50,1.65 and 1.90. The durability of the glass with an index of refractionof 1.9 is not as good as the soda glass retro-reflector.Retro-reflectors with a refractive index of 1.90 are generally called,“airport beads,” and are used to mark runways at airports.

Retro reflectivity is dependent upon the immersion level on the bead,particle, or phosphor. Optimum level of retro-reflector beads is 50-60%,assuring optimum imaging. Increasing immersion beyond 60% significantlydecreases the amount of light that can be directed back to thereceiver/laser. Typically this coating is obtained when the bead is setinto a paint or polymer.

The problem of cargo security is global. Some reported numbers include

Airport/Port Security

-   -   9,618,337 departed flights in a recent year    -   63,800 Cargo ship port calls in 2007

Cargo Containers

-   -   $12.5 Trillion of cargo is moved each year in ˜200 million        containers    -   Globally, 2% are inspected    -   Nearly $50 billion a year is lost to high-value cargo theft

Border Control

-   -   41,694,587 pedestrians crossed US borders in a recent year    -   6,626,007 loaded truck containers    -   194,525,561 passengers in personal vehicles        Illegal immigrants are estimated at 12 million, almost 1 in        every 20 workers with∘26 tunnels in 2009, 16 in 2008 with a 60%        increase in tunneling.

Product Counterfeiting

The overall cost of counterfeiting in the world was about 5-7% of worldtrade (some estimates put this at $176-250 billion)

SUMMARY OF THE INVENTION

As the beads herein retro-reflect very little visible light they are noteasily seen in visible light; thus they are difficult to counterfeit.Even if smugglers or thieves know the beads are there, it is difficultto get approximately the same bead content and same non-visibleretro-reflection as in adjacent original paint.

As, e.g., an anti-counterfeiting tool, a mixture of different types ofbeads can be used; types can include: Interrogatible by IR, UV, or both;Half-reflective coated or not; Reflective of the interrogatingwavelength, or at least one modified wavelength.

Further, beads can be directly placed a surface or loose inside acontainer. The surface can be at least one of on the container, onlabel, and on security tag. Overt and covert beads can be mixed tofurther confuse counterfeiters.

This can be a method of producing a spheroid retro-reflector which isretro-reflective to interrogating light outside of the visible spectraof radiation but is substantially non-retro-reflective of visible light,said method comprising: Providing a spheroid retro-reflector innerportion at least partially transparent to said interrogating light; andDepositing an outer layer of material over said inner portion, whereinsaid material substantially scatters or absorbs visible light and atleast partially transmits said interrogating light.

The outer layer of material can be a chalcogenide glass, silicon, aselenium glass or mixtures.

In some embodiments the interrogating light is infrared. In someembodiments the interrogating light is eye-safe.

In some embodiments the inner portion contains a nonlinear opticalmaterial, which may be a phosphor. In some embodiments the nonlinearoptical material is coated over said inner portion and is under theouter layer.

In some embodiments the retro-reflector is amorphous, e.g. glass orplastic.

The retro-reflector may be less than 1 mm in diameter, less than 0.1 mmin diameter less than 50 microns in diameter, or even less than 10microns in diameter.

This can also be a method of producing one or more retro-reflector beadsthat can be interrogated, said method comprising: providing a beadretro-reflector with an inner portion at least partially transparent tointerrogating light; and a non-linear optical material is in the bead,coated on the bead and/or in a binder that binds said beads to asubstrate. The nonlinear optical material may be at least one of aninorganic phosphor, an organic phosphor, a liquid-crystal polymer, and asingle crystal or polled solid solution material.

This may also be a method of interrogating a spheroid retro-reflectorwith interrogating light, said method comprising: Providing a spheroidretro-reflector inner portion at least partially transparent to saidinterrogating light; and Providing visible-light substantiallyscattering or absorbing material and at least partially transmits saidinterrogating light in an outer layer of material over said innerportion or within said inner portion, wherein said interrogating lightis retro-reflected and the visible spectra of radiation is notsubstantially retro-reflected.

This can be a method of producing a spheroid retro-reflector which isretro-reflective outside of the visible spectra of radiation but issubstantially non-retro-reflective of visible light.

The retro-reflector element may be of a design where half of the elementmay be coated with a reflective coating. The inner portion of theretro-reflector element is generally at least partially transparent tothe interrogating light. An outer layer of material is applied uniformlyaround the retro-reflective element. The coated retro-reflective elementcan have a dull appearance in visible spectra but be transparent in theinfra red spectra. Once such coating is silicon. For long rangeinterrogation a coherent light source is preferable. As used herein, theterms “spheres” and “beads” include oblate spheroids, prolate spheroids,as well as spheres.

This can also be a method of producing one or more retro-reflector beadsthat can be interrogated by selective light (e.g. a selective lightinterrogatible retro-reflector spheroid), said method comprising:providing a bead retro-reflector with an inner portion at leastpartially transparent to interrogating light; and depositing an outerlayer of material over said inner portion, wherein said materialsubstantially scatters or absorbs visible light and at least partiallytransmits said interrogating light.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the figures, inwhich:

FIG. 1 shows prior art pavement markings with reflective beads at nightwhen illuminated with visible light from automobile headlights;

FIG. 2 shows prior art pavement markings without reflective beads atnight when illuminated with visible light from automobile headlights;and

FIG. 3 shows prior art with one ray of light being retro-reflected by aspherical particle.

DETAILED DESCRIPTION OF THE INVENTION

As the beads retro-reflect very little visible light they are not easilyseen in visible light; thus they are difficult to counterfeit. Even ifsmugglers or thieves know the beads are there, it is difficult to getapproximately the same bead content and same non-visibleretro-reflection as in adjacent original paint.

As an anti-counterfeiting tool, a mixture of different types of beadscan be used; types include: Interrogatible by IR, UV, or both (covertmaterial can be coated on, or put in the beads, and can keep not onlyvisible light from retro-reflecting, but either IR or UV, as well);Half-reflective coated or not (retro-reflections from half-reflectivecoated bead can be much brighter); Reflective of the interrogatingwavelength or at least one modified wavelength (e.g. from nonlinearmaterials such as phosphors).

Further, beads can be directly placed a surface or loose inside acontainer. The surface can be at least one of on the container, onlabel, and on security tag. Overt and covert beads can be mixed tofurther confuse counterfeiters.

Cargo containers are generally inspected and sealed prior to shipping.If the seal is in place and the container does not appear to be damaged.Then the containers are generally not re-inspected until arrival attheir final destination unless the container appears damaged. Modernsmugglers and thieves, however, have cut the doors of the containers,welded them, and then repainted them to avoid tampering with the seal.Placing the bead-containing paint tag in the original paint of the cargocontainers allows easy detection of where smugglers or thieves havecovered the welds or other damaged regions of the cargo container withconventional paint.

As the beads are not easily seen in visible light, they are difficult tocounterfeit. Even in the smugglers or thieves know the beads are there,it is difficult to get the same type or types of bead as in the originalpaint. Thus a medium density of beads is generally preferred.

As used herein the terms “bead” or “beads” refer to—retro-reflectorbead—or—retro-reflector beads, unless otherwise indicated.

Beads can be used over at least of a portion of a label and/or asecurity seal, and/or at least a portion of the container. In someembodiments, tape used to seal boxes can be use as a security seal. Thebeads can be applied as a barcode, as covert barcoded labeling ofcontainers can add an extra level of security. Products exist that haveprinting or bar codes and tape that cannot be resealed. However, thereare no current products that provide easily detection of tampering orcounterfeiting.

Tampering can be detected using these beads to determine, e.g., if acontainer has been redirected, and/or if something has been removedand/or inserted in the container.

If missing containers are found later in some other location, beads canprovide evidence that the containers had been stolen. Tagging on sixfaces of a box can make the stolen box easier to find.

The bead content of liquid paint before being painted, as compared tothe normal bead content in commercially used reflectorized paint, can bevaried from relatively low, up to commercially used content. Use ofvarying content can make counterfeiting more difficult; as; e.g.,matching the bead density and types of beads on a counterfeit securityseal to the bead density on the original container is not easy.

Beads may be applied through one or more stencils to give the beads adistinctive pattern.

Spotted or textured retro-reflections over an area are generallypreferred in most embodiments as being less expensive and more covert.Spotted or textured retro-reflections over an area can utilize fewerbeads.

In some embodiments, there can be a mix of protected and unprotectedcontainers; where the protected containers have beads that aredetectable with at least one of IR and UV light.

For remote detection; i.e. 5 foot or more, interrogation is preferablydone with IR; in some embodiments, detected containers are furtherexamined at near range for indications of tampering with at least one ofIR and IJV light.

In some embodiments, protected containers preferably have at least oneof covert retro-reflective beads and covert retro-reflective withhalf-reflective-coated retro-reflectors.

In some embodiments, an at least one of IR and UV detectable marking isapplied over at least a portion of a label and at least a portion of thecontainer.

In some embodiments, a covert barcode is used to verify a visiblebarcode; e.g. the covert barcode can match or be a mathematical functionof the visible barcode.

Covert retro-reflecting beads and mixtures of different types of beadscan be used.

A mixture of retro-reflecting bead types can include, e.g., coatedretro-reflecting UV and/or IR beads; with or without UV and/or IRphosphors; areas with some plain-glass beads and areas with bothplain-glass and half reflective coated beads, more than two types ofbeads, and other mixtures of bead types.

Customized retro-reflecting bead types and patterns can be used bydifferent shippers to help in sorting containers and to confusecriminals. Detection of tampered packages at stages, e.g. both incomingand outgoing, can be used to localize where tampering had occurred.

Loose beads inside of container to indicate who may have opened thecontainer, e.g. with IR phosphor [catch them (infra)-red handed]. Thiscould be done with bait containers to help trapping of thieves.

Note that unlike highway paint of FIG. 1 where plain glass spheresappear as solid, these retro-reflecting bead loadings reflections inmany embodiments preferably appear to be a number of individual dots;just has to be enough beads to look suspicious when tampering hasoccurred.

Retro-reflecting beads applied to surface can also be, e.g. dusted onand covered with clear tape; printed on, e.g. address label, securityseal, or barcode, e.g. with bead-containing ink.

This general approach makes detection of covert beads and counterfeitingdifficult, as it can require special equipment, and be time-consumingand more risky for thieves and smugglers.

Coated beads or retro-reflectors can include retro-reflective beads orwith covert, half-reflective, and phosphor-containing coatings, andcombinations thereof.

Coated retro-reflectors can be applied with clear binders, e.g. ink,paint, and/or tape. These are preferably interrogated with at least oneof IR and IN light from a non-vertical angle, e.g. and angle of 30 to 60degrees from vertical.

Diffused at least one of IR and UV light reflected off the substrate towhich the coated retro-reflectors are applied can make interrogationmore difficult, but can be reduced by an at least one of IR and UV lightabsorbing substrate. If the beads have only a covert coating, the amountof retro-reflection depends on the difference of index of refractionbetween the bead and the binder, and thus covert coatings with at leastone of half-reflective and phosphor-containing coatings, are preferred.

As the light is focused to the back of the spherical retro reflector thepeak power density increase and the efficiency/brightness of the nonlinear media/phosphor in the sphere or on the surface of the sphere willincrease dramatically.

In some embodiments, the beads are dusted on and then covered, e.g. witha spray of clear paint or with clear tape. Glue may be applied, e.g. ina pattern, to a substrate (e.g. printed, through a stencil, or with aglue stick), and the beads dusted over the glue. The beads may also bedusted over the glue side of clear tape, with or without a pattern andthen the tape applied to a substrate.

The non-visible light used in interrogating the bead may be UV and/orIR. Infra red is preferred for many embodiments. Ultraviolet may be usedto allow the use of a large number of narrow-band-emitting phosphors,whose retro-reflections can be distinguished from one another.

This includes a security tag of a proprietary coating layer containingsmall particles, preferably spherical beads and preferably sprayedand/or painted on; and also interrogation of the beads. Beads that arepainted-on from a liquid or sprayed typically are just a random patternof beads within the painted area.

This security tag can include a bead design with a bead coating that canmake beads look like dust or dirt to the eye; this combined with thelimited viewing angle for the non-visible, e.g. IR, retro reflectionsignal can make counterfeiting of tags very difficult.

Multiple combinations of multiple different-property security tags canadd to the difficulty of counterfeiting, and even finding any or all ofthe tags. Depending on the value of the cargo, the tagging can be variedfrom one inexpensive single tag to multiple combinations of multipledifferent-property tags.

Beads can be produced in high volume e.g. by liquid-phase depositions,e.g. half-reflectors in a 4 step process.

FIG. 3 shows one ray of visible light being retro-reflected by aspherical bead as has been done in the past, but this figure can be alsobe used better understand retro-reflected IR and/or UV light and(half-coated with an IR and/or UV reflector) used in accordance with themethod herein.

If the bead has a coating as described herein, to block visible lightbut is not half-coated with an IR and/or UV reflector, theretro-reflection can be much less, depending on the IR and/orreflectivity of the paint, but even with black paint can still be about4% and can be detected.

FIG. 3 can also help explain the focusing of light on the backside of asphere as used herein. If both of two rays of light shown are incominglight from an interrogation lamp that is larger in diameter than thebead, as is normally the case, both incoming rays converge on a smallspot, increasing the intensity. Basically the image of an IR, visible,or UV light source can be focused on the back side of a bead and theenergy can be concentrated in a small area of high intensity.

Thus phosphors and other non-linear optical material can be efficientlyenergized. Phosphors and other non-linear optical material can changethe wavelength such that the wavelength of at least a portion of theretro-reflected light is different from that of the interrogating light.

As can also be seen from FIG. 3, the rays are converging within thebead, and thus the area is decreasing and the intensity is rising. Thusphosphors and other non-linear optical material used herein can bewithin the bead and be efficiently energized, including being energizedsufficiently for 2-photon reactions.

Especially with phosphors and other non-linear optical materialembodiments, the phosphors and other non-linear optical material can bein the bead, coated on the bead, generally under the outer layer, and/orin the binder.

Especially in near field applications, less than about 5 feet,retro-reflectors with internal phosphors and other non-linear opticalmaterial can be used with visible light as well.

Being covert is not always advantageous is such applications, and beingovert may be advantageous in some. The interrogating light in suchapplications can be IR, visible, and/or UV and the detected light canalso be IR, visible, and/or UV light. Thus in some embodiments, theinterrogating light can be IR or visible, and the detected light bevisible. With stripes of heads, shining interrogating light on an areaof one color could make the area appear to have striping with adifferent color and detected without special equipment.

Nonlinear optical materials can be organic and inorganic materials. Theinorganic materials can be single crystal or polled solid solutionmaterials; including but not limited to: KTP, RTP, LBO, BBO,periodically poled LiNbO₃, stoichiometric LiTaO₃, and KTP, PLZT, PZT,KTN; and phosphors BaMgAl10O17:Eu2+ (BAM), Y203:Eu, and ZnS-basedphosphors such as ZnS:Mn.

Nonlinear organic materials can also include organic phosphors (see U.S.Pat. No. 3,867,302 ORGANIC PHOSPHORS AND PROCESS FOR PRODUCTION THEREOFby Takano et al, and U.S. Pat. No. 5,100,580 PHOSPHORESCENT MATERIALS byPowell, et al), or Liquid Crystal materials.

Liquid-crystal polymers (LCPs) are a class of aromatic polyesterpolymers. A unique class of partially crystalline aromatic polyestersbased on p-hydroxybenzoic acid and related monomers, liquid-crystalpolymers are capable of forming regions of highly ordered structurewhile in the liquid phase. However, the degree of order is somewhat lessthan that of a regular solid crystal. Typically LCPs have a highmechanical strength at high temperatures, extreme chemical resistance,inherent flame retardancy, and good weatherability. Liquid-crystalpolymers come in a variety of forms from sinterable high temperature toinjection moldable compounds. LCP can be welded, though the linescreated by welding are a weak point in the resulting product. LCP has ahigh Z-axis coefficient of thermal expansion.

LCPs are exceptionally inert. They resist stress cracking in thepresence of most chemicals at elevated temperatures, including aromaticor halogenated hydrocarbons, strong acids, bases, ketones, and otheraggressive industrial substances. Hydrolytic stability in boiling wateris excellent. Environments that deteriorate the polymers arehigh-temperature steam, concentrated sulfuric acid, and boiling causticmaterials.

Beads can be made with different reflection properties. Modified tagscan be routinely introduced, e.g, ever 9 to 12 months, to minimizecounterfeiting of tags; or even sooner if counterfeiting is detected.

High value cargo can be marked with special beads, includingphosphor-containing and/or other non-linear optical material beads. Anumber of different phosphors and/or other non-linear optical materialscan be used in a very large number of combinations.

In some embodiments, the covert bead retro-reflectors have hemisphericalreflective coatings. Interrogation of beads may be performed using acoherent laser light source (e.g. eye-safe 1,550 nm). Interrogation ofbeads may be performed using low power, e.g. <0.5 W for shorter rangefinder source for near field detection.

A higher power, e.g. 5W, laser source can be used for far field, atleast about 5 foot, remote detection. Low divergence angle ofretro-reflection minimizes detection of reflections by others, such ashijackers; such detection is also minimized by the use of non-visiblelight.

Existing laser imaging arrays and eye glasses can be used for detectionof the non-visible light, and with some nonlinear optical materials,beads can return modified wavelengths in the visible region.

Commercial cargo-containers, including vehicles, can be painted withpaint caring tags as such any modification or substitution of them canbe easily detected.

Single or multiple tags, in one or more various locations, patternedand/or unpatterned, painted directly on a container and/or on itemsattached to the container, can be used. Thus, for example, theretro-reflector tags can be used, e.g. painted, on the security-seals ofcargo doors of rail-cars, ships, or trucks and on containers in theircargo, and these tags can be detected while the vehicles or cargo are inmotion. The inquiry of tags can be with eye-safe IR and thus withoutharming personnel in the interrogation beam.

As used herein, a “label” can have an address, a barcode, or be at leasta portion of a security seal. As used herein, a covert bead means a beadthat generally retro-reflects at least one of IR or UV light whilegenerally avoids retro-reflecting of visible light.

As used herein, “bead” or “beads” mean retro-reflector orretro-reflectors which are reflective of IR/UV light and/or of lightfrom a phosphor activated by IR/UV light unless otherwise indicated.

Retro-reflectors reflect undiffused light back toward the source oflight, while clear layers only reflect undiffused light back toward thesource when the source is near perpendicular to the surface.

As used herein, “IR/UV” means at least one of IR or UV light. As usedherein, “half-reflective” means that a reflective coating covers fromabout 25% to about 50% of the surface, e.g. the bottom half of a bead.As used herein, “retro-reflective” means retro-reflective of IR/UV lightand/or of light from a phosphor activated by IR/UV tight unlessotherwise some embodiments indicated. As used herein, a “label” can havean address, a barcode, or be at least a portion of a security seal. Asused herein, a covert bead means a bead that generally retro-reflects atleast one of IR or UV light while generally avoids retro-reflecting ofvisible light. As used herein, “bead” or “beads” mean retro-reflector orretro-reflectors which are reflective of IR/UV light and/or of lightfrom a phosphor activated by IR/UV light unless otherwise indicated.

Retro-reflectors generally reflect undiffused light back toward thesource of light, while clear layers only reflect undiffused light backtoward the source when the source is near perpendicular to the surface.Nonlinear materials

As used herein, “IR/UV” means at least one of IR or UV light. As usedherein, “half-reflective” means that a reflective coating covers fromabout 25% to about 50% of the surface, e.g. the bottom half of a bead.As used herein, “retro-reflective” means retro-reflective of IR/UV lightand/or of light from a phosphor activated by IR/UV light unlessotherwise some embodiments indicated.

As used herein, the terms “IR detectable” or “UV detectable” mean that ausable signal can be produced when interrogated by IR or UV light.

Beads can be used over at least of a portion of a label, barcode, and/ora security seal, and/or at least a portion of the container to allowvisible (e.g. with IR glasses) indication of tampering. In someembodiments, tape used to seal boxes can be use as a security seal.

Tampering detection using these beads can determine, e.g., if acontainer has been redirected, and/or if something has been removedand/or inserted in the container.

If missing containers are found later in some other location, beads canprovide evidence that the containers had been stolen. Tagging on sixfaces of a box can make the stolen box easier to find.

The bead content of liquid paint before being painted, as compared tothe normal bead content in commercially used reflectorized paint, can bevaried from relatively low, up to commercially used content. Use ofvarying content can make counterfeiting more difficult, as, e.g.,matching the bead density on a counterfeit security seal to the beaddensity on the original container is not easy.

The non-visible light used in interrogating the bead may be UV and/orIR. Infra red is preferred for many embodiments. Ultraviolet can be usedto allow the use of a large number of narrow-band-emitting phosphors,whose retro-reflections can be distinguished from one another.

Co-filed applications TIA-2 and TIA-3 are hereby incorporated byreference herein. Although the present invention and its advantages havebeen described above, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the invention as defined by the appended claims.Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification, but only by the claims.

What is claimed is:
 1. A method of producing a spheroid retro-reflectorwhich is retro-reflective to interrogating light outside of the visiblespectra of radiation but is substantially non-retro-reflective ofvisible light, said method comprising the steps of: providing a spheroidretro-reflector inner portion at least partially transparent to saidinterrogating light outside of the visible spectra of radiation; anddepositing an outer layer of material over said inner portion, whereinsaid material substantially scatters or absorbs visible light and atleast partially transmits said interrogating light outside of thevisible spectra of radiation.
 2. The method of claim 1, wherein saidouter layer of material is chalcogenide glass.
 3. The method of claim 1,wherein said outer layer of material is silicon.
 4. The method of claim1, wherein said outer layer of material is selenium glass.
 5. The methodof claim 1 wherein said interrogating light outside of the visiblespectra of radiation is infrared.
 6. The method of claim 1, wherein saidinterrogating light outside of the visible spectra of radiation iseye-safe.
 7. The method of claim 1, wherein said inner portion containsa nonlinear optical material.
 8. The method of claim 7, wherein saidretro-reflector contains a phosphor.
 9. The method of claim 7, wherein anonlinear optical material is coated over said inner portion and isunder said outer layer.
 10. The method of claim 1, wherein saidretro-reflector is amorphous.
 11. The method of claim 1, wherein saidretro-reflector is less than 1 mm in diameter.
 12. The method of claim1, wherein said retro-reflector is less than 50 microns in diameter. 13.The method of claim 1, wherein said retro-reflector is less than 10microns in diameter.
 14. The method of claim 1, wherein saidretro-reflector is less than 0.1 mm in diameter.
 15. A method ofproducing one or more retro-reflector interrogated beads at leastpartially transparent to interrogating light outside of the visiblespectra of radiation comprising the steps of: providing a beadretro-reflector with an inner portion at least partially transparent tointerrogating light outside of the visible spectra of radiation; and anon-linear optical material is in the bead, coated on the bead and/or ina binder that binds said beads to a substrate.
 16. The method of claim15, wherein said nonlinear optical material is at least one of aninorganic phosphor, an organic phosphor, a liquid-crystal polymer, and asingle crystal or polled solid solution material.
 17. A method ofinterrogating a spheroid retro-reflector with interrogating light, saidmethod comprising: providing a spheroid retro-reflector inner portion atleast partially transparent to said interrogating light outside of thevisible spectra of radiation; and providing visible-light substantiallyscattering or absorbing material and at least partially transmits saidinterrogating light outside of the visible spectra of radiation in anouter layer of material over said inner portion or within said innerportion, wherein said interrogating light outside of the visible spectraof radiation is retro-reflected and the visible spectra of radiation isnot substantially retro-reflected.
 18. The method of claim 17, wherein amixture of at least three types of beads is used, wherein types areinterrogatible by IR; interrogatible by UV; interrogatible by both IRand UV; half-reflective coated; reflective of the interrogatingwavelength; and reflective of at least one modified wavelength.